The present invention relates to a flap folding device of a wrapping machine for over-wrapping, with a wrapping sheet like kraft paper, an approximately rectangular content such as a stack of paper or a number of books, or belt-like cloth or textile folded longitudinally in a staggered form, or a stack of a number of boxes and, more particularly, to a flap folding device in which a pair of side-folding guides are arranged on the same plane as the open side of an approximately rectangular content whose body portion has been wrapped with the wrapping sheet in a tubular form, and move into contact with, and away from, both side flaps at each protruding end of the wrapping sheet projecting in a square cylindrical form from the open side; as the side-folding guides contact the side flaps, the side flaps are folded inward along the open side of the content, and subsequently remaining lower and upper flaps at each protruding end are folded in order along the open side of the content.
As this type of flap folding device of a wrapping machine, there has been known such a device that, as disclosed in Japanese Utility Model Laid-Open No. Hei 3-32004, projections are provided facing the vicinity of the upper and lower ends of each side flap by forming each side-folding guide a little smaller in a vertical size than that of the content to be wrapped. These side-folding guides approach both side flaps, where the upper and lower projections hit against the vicinity of the upper and lower ends of each side flap and then move horizontally along the open side of the content to be wrapped, thereby pushing the upper and lower ends of the side flaps straight from the base end to the forward end. Then, each side flap is folded at a right angle at the base end until the whole part of the side flap will be flat against the open side, and at the same time, the lower flap and the upper flap are added with a horizontal folding line while being folded obliquely at 45 degrees at both side ends; and subsequently the lower flap and the upper flap are protruded out horizontally through a clearance formed vertically in the side-folding guide.
Furthermore, as disclosed in Japanese Utility Model Laid-Open No. Hei 2-23305, each side-folding guide is composed of a pair of upper and lower plates, which are horizontally rotatably installed such that a clearance between the upper and lower plates will be adjustable in accordance with a change in the vertical size of the content; these side-folding guides rotate nearly simultaneously until they hit against the vicinity of the upper and lower ends of both side flaps. Thereafter, the side-folding guides are horizontally moved along the open side of the content, pushing the upper and lower ends of both side flaps as in a straight state from the base end to the forward end while folding each side flap at the base end at a right angle until the whole part of the side flap is flat against the open side. At the same time, the lower flap and the upper flap are folded at both side ends, at 45 degrees, to produce a horizontal folding line, thus being protruded out horizontally.
Furthermore, as disclosed in for example Japanese Patent Publication No. Hei 3-14685, with a content placed on a wrapping sheet which has been fed on an elevator, a switch is manually operated to thereby lower the elevator to fold up the wrapping sheet in a nearly U shape. Thereafter, the wrapping sheet is horizontally transferred by a transfer means from the elevator to a discharge table, where both ends of the folded wrapping sheet are lapped over the upper surface of the content, thus finishing the body wrapping process. At the same time, the side flap positioned on the upstream side in the direction of transfer of each protruded end is folded, by the side-folding guide connected by the transfer means, along the open side of the content, and then the side flap positioned on the downstream is folded along the open side of the content by a fixed side-folding guide. Thereafter, the upper flap is folded down along the open side and at the same time an adhesive tape fed out by a tape feeding mechanism is attached by a taping mechanism on both overlapped ends of the wrapping sheet to close these overlapped ends. Subsequently, after the upward folding of the lower flap along the outer side of the upper flap that has been folded, the forward end of the lower flap which has been overlapped on the extreme outer side by the inward protruding motion of the guide is folded along the upper surface of the content, and then the adhesive tape fed out by the tape feeding mechanism is affixed on the forward end of the lower flap and on the upper surface of the content to seal them.
These prior-art flap folding devices of the wrapping machine described above, however, have such a problem that the side-folding guide simply moves horizontally along the open side of the content to be wrapped, to push to fold the upper and lower ends of the side flap as in a straight state, and therefore the side flap facing the closed side of the wrapped body of the content is likely to swell at the vicinity of the base end because of its nerve when the side flap is folded at the base end; particularly the looser the body is wrapped, the larger the side flap swells, with the result that the whole part of the protruding end can not be folded in along the content. Particularly when a corner part formed between the closed side of the wrapped body of the content and the open side is chamfered to an oblique or circular form, unstable side flap folding easily occurs, resulting in deteriorated appearance and lowered commodity value.
Furthermore, the side flap is folded at two places, upper and lower, by the side-folding guide; therefore, when the height of the content has been changed, it will become necessary to change the vertical size of the side-folding guide according to the change, and also to make the positional adjustment of the side-folding flap so that the side-folding guide will face the upper and lower ends of the side flap. The flap folding device, therefore, has the problem that it is not easily adjustable and usable, and furthermore becomes complicated in structure due to the adoption of the side-folding guide adjusting mechanism and large in the size of the device on the whole.
Furthermore, the upper flap and the lower flap are folded obliquely at 45 degrees at both side ends when the whole part of either of the side flaps is folded; therefore in the case of the so-called normal folding that each protruding end protrudes shorter than a half of the width of the open side of the content, the upper and lower flaps are folded separately and obliquely at 45 degrees without folding lines interfering with each other. Especially in the case of the so-called overlap folding that each protruding end protrudes longer than a half of the width of the open side of the content, the forward end of these 45-degree oblique folding lines meet within the upper and lower flaps, interfering with each other. Accordingly the forward ends of the upper and lower flaps can be folded without resistance; if, therefore, the flaps are folded forcibly, the wrapped article will have a bad outward appearance, resulting in a lowered commodity value.
Consequently, in the case of the so-called overlap folding that the length of projection of each protruding end becomes greater than a half of the width of the open side of the content from a dimensional relation between the content and the wrapping sheet, a decision will be made that flap folding is impossible, excluding the overlap folding part from the normally foldable range; then for example the size of the wrapping sheet will usually be changed to allow the so-called normal folding that the length of projection of each protruding end becomes less than a half of the width of the open side of the content. However, even this type of wrapping is impossible where very few kinds of wrapping sheets suitable for normal folding are available.
Furthermore, there is also the following problem. Each side-folding guide, after hitting against each side flap, moves horizontally along the parallel open sides of the content; therefore when the content, being light in weight, easily moves, the content is likely to move off the mounting position with a shock caused by the hitting of each side-folding guide against the side flap. And also if the content supplied has moved off the mounting position due to for example a dimensional error of the content, the mounting position of the content will further move away from a proper position because of a shock caused by the hitting of the side-folding guide against the side flap. Particularly if the hitting timing of the side-folding guide which hits against the side flap is shifted, the content easily moves off position, resulting in a defectively folded side flap.
In the prior-art wrapping machine, both the so-called fold-down wrapping for folding down the forward end of the upper flap on the outermost side along the underside of the content and the so-called fold-up wrapping for folding up the forward end of the lower flap on the outermost side along the upper side of the content are not performed by a single flap-folding device; that is, either of the fold-down wrapping and the fold-up wrapping requires an exclusive device for itself. The adoption of separate flap-folding processes for fold-down and fold-up wrapping, however, presents the problem that the device on the whole will become large in size.